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Racial Differences in Heart Rate Variability During Sleep in Women:
The Study of Women Across the Nation Sleep Study
Hall MH, Middleton K, Thayer JF, Lewis TT, Kline CE, Matthews KA, Kravitz HM, Krafty RT, Buysse DJ

Although the number one cause of death for women in the United States is cardiovascular disease, few studies of heart rate variability have specifically analyzed women.  Likewise, there has also been a dearth of studies examining heart rate variability during sleep as opposed to during awake hours.  Dr. Martica Hall and her colleagues used data from the Study of Women Across the Nation (SWAN) study to investigate these under-researched areas. 

The SWAN Sleep Study was conducted over a five-year span beginning in 2002 and included 368 participants.  These participants were of African American, Chinese American, and European American heritage, as determined by the study participants themselves.  Researchers analyzed participants? sleep using self-reported sleep diaries as well as in-home polysomnography, both of which measured three consecutive nights of sleep.  

Dr. Hall and her colleagues examined the relationship between heart rate variability and race for the women who participated in the study.  After accounting for statistical abnormalities, they found significant differences in heart rate variability among the three groups studied for both non-rapid eye movement and rapid eye movement Stage 2 sleep.  European American women had significantly lower normalized high-frequency heart rate variability in relation to African American and Chinese American women in the study.  Additionally, European American women also showed greater low-to-high frequency heart rate variability ratios during sleep than African American and Chinese American women.  Based on these results, the researchers concluded that there is indeed a substantial relationship between race and heart rate variability during sleep.  European American women displayed lower vagally mediated control of the heart during sleep as compared to African American and Chinese American women.  Further research is warranted and imperative, in order to determine whether heart rate variability during sleep, along with the racial differences demonstrated, could be a predictor of cardiovascular disease.

Contributors:  
Martica H. Hall, PhD; Christopher E. Kline, PhD; Karen A. Matthews, PhD; Daniel J. Buysse, MD (Department of Psychiatry, University of Pittsburgh)

Kellie Middleton, MD, MPH (Department of Surgery, University of Pittsburgh)

Julian F. Thayer, PhD (Department of Psychology, Ohio State University)

Tené T. Lewis, PhD (Rollins School of Public Health, Emory University)Howard M. Kravitz, DO, MPH (Departments of Psychiatry and Preventive Medicine, Rush University Medical Center)

Robert T. Krafty, PhD (Department of Statistics, Temple University)

The results of this investigation were published in Psychosomatic Medicine.  Click here for a link to the abstract.